On Wed, Jul 18, 2018 at 10:38:27AM -0700, Dave Hansen wrote: > On 07/17/2018 04:20 AM, Kirill A. Shutemov wrote: > > Pages encrypted with different encryption keys are not allowed to be > > merged by KSM. Otherwise it would cross security boundary. > > Let's say I'm using plain AES (not AES-XTS). I use the same key in two > keyid slots. I map a page with the first keyid and another with the > other keyid. > > Won't they have the same cipertext? Why shouldn't we KSM them?
We compare plain text, not ciphertext. And for good reason. Comparing ciphertext would only make KSM successful for AES-ECB that doesn't dependent on physical address of the page. MKTME only supports AES-XTS (no plans to support AES-ECB). It effectively disables KSM if we go with comparing ciphertext. -- Kirill A. Shutemov
